This invention relates to lock and key sets, and more particularly, to a lock and key set including a tamper resistant, free-wheeling type lock.
The purpose of a free-wheeling type lock is well known in the industry and various designs can be seen in the marketplace. The construction of a free-wheeling type lock prevents the lock from being over-torqued during an attack by allowing the lock cylinder to de-clutch from the driving mechanism of the lock when an improper key, screwdriver or other device is used to turn the lock cylinder. To reset the lock, the cylinder is rotated back to a key-out position where the lock cylinder is again coupled to the driving mechanism. Although many concepts have been explored in the past, most free-wheeling locks have been costly and complicated to produce or have proven to be unreliable. Many designs are bulky in size or require multiple motions of the key, including various push in and turn sequences, to actuate their drive mechanisms.
Typically, free-wheeling type locks include a spring-loaded detent to achieve the clutching action between the moving parts of the lock. However, the use of a spring-actuated motion to move the internal mechanisms results in a non-positive motion that is subject to timing restraints. Some free-wheeling lock designs fail to isolate the tumblers from the rotary motion of the sleeve tumbler ward, making the locks more susceptible to picking. Most locks can be picked when the cylinder is rotated with respect to the sleeve or case tumbler ward. This allows a tumbler to be "loaded" or to contact the edge of the sleeve or case tumbler ward. When the tumblers are held in this manner, the tumblers can be individually picked down out of the ward and rotated forward ever so slightly and be retained in place by the sleeve or case edge until the cylinder rotates freely. Some known free-wheeling locks include a sleeve which rotates with respect to the cylinder but typically have a spring biased detent ball which holds the sleeve in the key-out position. This detent allows enough drag on the sleeve to permit an attacker to load a tumbler and permits picking.
To accommodate the multiple motion key sequences, known free-wheeling locks provide for axial displacement of the cylinder and/or the sleeve. The displacement is usually against the force of a spring bias to allow the cylinder and/or the sleeve to be returned to the key-out position when torque or axial motion on the key is released. However, the requirement for spring bias and additional motion can make the lock complicated to use.
Another consideration is that locks can be compromised by slam-pulling the lock cylinder, out of the case, exposing the driving mechanism. Although slampull preventing designs have been proposed, many have not been successful. Thus, known locks generally do not prevent manipulation of the drive mechanism after a slam-pull attack.
It is, therefore, an object of the invention to provide a new and improved lock and key set.
Another object of the invention is to provide a free-wheeling lock which is pick resistant.
A further object of the invention is to provide a free-wheeling lock which is rendered inoperative if the cylinder is forcibly removed from the lock, such as by being slam-pulled from the case.
Another object of the invention is to provide a free-wheeling lock which does not require multiple motions of the key to actuate the drive mechanism of the lock.
Another object of the invention is to provide a mechanism that will disengage the cylinder from the drive mechanism when subjected to a forced rotation.
Yet another object of the invention is to provide a free-wheeling lock in which the tumblers are isolated from the rotary motion of the sleeve tumbler ward.
Another object of the invention is to provide a free-wheeling lock which is compact in size and requires few components.